In the bioscience fields with intensifying researches, millions of experimental small animals (e.g., mice, rats and the like; hereinafter referred to as small animals) such as conventional animals, SPF animals, gnotobiotic animals and germfree animals are subject to research, experimentation, inspection, and the like every year. As the modification of genes is facilitated regardless of the size of facilities, hundreds of thousands of small animals are produced at hundreds of research institutions in the nation throughout the year. Furthermore, delivery and receipt of those small animals are performed frequently and broadly between such research institutions, and the small animals are used for research and experimental purposes.
Under existing circumstances, however, breeding and reproducing of small animals are conducted at various places from a breeding and experimenting facility in a clean environment with highly controlled air conditioning (hereinafter, referred to as a facility) to an ordinary small room or the like with no control of air conditioning. Thus, there occur variations in the microbiological quality of such small animals, which have great and negative influences on research and experiments and which also causes problems regarding qualification of small animals that may be used as a subject of research or experimentation.
For example, if small animals contaminated with pathogenic microbes are brought to a facility, the entire facility will be a new source of contamination, and for cleaning the facility, it will cost several hundred million yen and take labor to dispose of all the small animals and to disinfect and improve the facility. Furthermore, a time loss of between three months and nearly a year is required for the cleaning of the facility environment and causes a very great deal of lost progress to research.
In order to avoid such circumstances, a quarantine inspection (mainly visual inspection on the conditions of the animals, and the like) or preparation and attachment of a monitoring report or the like (hereinafter, referred to as a certificate) are conducted upon delivery and receipt of those small animals. However, this certificate merely indicate under what conditions such small animals being delivered were bred, and never guarantees the microbiological quality of the individual small animals.
Thus, what is initially important is to confirm that animals with a specific quality and being subject to a specific biological experiment (referred to as a subject animal), such as mice with specific genetical modification, animals bred in a germfree condition regardless of their genes, or animals infected with specific bacteria, are not infected with any disease, or the animals are not infected with some kind of microorganism. The cage according to the present invention is used for such a confirmation.
The subject animals are bred in various different environments and brought into research institutions as animals with a specific quality; however, it is not certain whether that would be true.
Of course, even if the subject animals are confirmed as being infected, there is a possibility that such infected animals will not influence the ultimate purpose of the subject animals, i.e., biological experiments. However, confirmation experiments using a cage have meaning in a sense that the fact of the subject animals being infected with some microorganism remains as data for this cage.
Furthermore, in a case where an intended biological experiment is genetic modification or the like when the subject animals are genetically-modified animals, even if the subject animals are infected with some kind of microorganisms, or they are infected with some disease, it is often that there is no influence from the genetic point of view to the experiment. Thus, researchers proceed with the intended experiment with no concern about the microorganic infection or disease. As a result, a problem of infection to other subject animals will occur, which may reduce the accuracy of biological experiments with the other subject animals.
However, the use of the cage according to the present invention allows the presence of infectious microorganisms or diseases to be detected, thereby inhibiting their influence of other subject animals. As a result, it becomes possible to increase the accuracy of biological experiments on the other subject animals.
Although there is no prior art to the present invention, which solves the problem as described above, prior art that is thought to be related even a little will be described below.
Japanese Laid-Open Publication No. 9-252676 (Patent Literature 1) discloses an experimental animal breeding apparatus configured such that a plurality of animal breeding cages are arranged in a breeding rack (hereinafter, referred to as a rack) and only the air that has passed through animals (which corresponds to the subject animals in the present invention) housed in the cages flows into a monitoring room in order to conduct microbiological monitoring (hereinafter, referred to as monitoring).
According to this apparatus, animals in the monitoring room breathe in the air that has had a contact with a plurality of animals in the cages. If there is an animal that is infected with microorganisms in the rack, the animals in the monitoring room will certainly be infected with the microorganisms. Thus, observation and inspection of the animals in the monitoring room allows an infection state of the animals in the rack to be confirmed promptly, and allows means of preventing the increase of infected animals to be immediately applied.
While this apparatus can detect pathogenic microorganisms of the infected animals in the monitoring room, it is not possible, however, to specify which animal is the source of infection because the animals have been infected through air that has passed through all the small animals in a plurality of racks. Furthermore, it is feared small animals in other adjacent cases will also be infected. Thus, it is necessary to take a large-scale measure for not only the small animals in the rack, but also all the other small animals in the entire facility for disposal, disinfection or the like.
Japanese Laid-Open Publication No. 2011-200154 (Patent Literature 2) and Housha-sen Kagaku, National Institute of Radiological Sciences, August 2007, Vol. 50, No. 8, pages 11 to 13 (Non-Patent Literature 1) discloses a sectioned animal cage used for testing of infection and the like among animals. This cage has a casing with an upper surface that can be opened, a dividing member made of a wire net arranged within the casing, and a lid that can be opened and closed and that is arranged at an opening part of each of two living spaces divided by the dividing member in the casing. Each lid is provided with a water tank and a feeding box.
However, when conditions of infection are monitored among small animals (which corresponds to the subject animals in the present invention) using the cage, there is a possibility of the infection being spread through the lid to the rack as well as the entire facility because the lid is made of a wire net to form a vent.